feat: reasoning model controller

src/semantic-router/pkg/extproc/reason_mode_selector.go

@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"log"
 	"strings"
+
+	"github.com/vllm-project/semantic-router/semantic-router/pkg/metrics"
 )
 
 // shouldUseReasoningMode determines if reasoning mode should be enabled based on the query category
@@ -45,6 +47,25 @@ func (r *OpenAIRouter) getReasoningModeAndCategory(query string) (bool, string)
 	return false, categoryName
 }
 
+// getModelFamilyAndTemplateParam returns a normalized model family name and the template param to be used (if any)
+func getModelFamilyAndTemplateParam(model string) (string, string) {
+	lower := strings.ToLower(strings.TrimSpace(model))
+	if strings.Contains(lower, "qwen3") {
+		return "qwen3", "enable_thinking"
+	}
+	if strings.Contains(lower, "deepseek") || strings.Contains(lower, "ds") {
+		return "deepseek", "thinking"
+	}
+	// GPT-OSS family and generic GPT fall back to using reasoning_effort (OpenAI-compatible field)
+	if strings.Contains(lower, "gpt-oss") || strings.Contains(lower, "gpt_oss") {
+		return "gpt-oss", "reasoning_effort"
+	}
+	if strings.Contains(lower, "gpt") {
+		return "gpt", "reasoning_effort"
+	}
+	return "unknown", ""
+}
+
 // getChatTemplateKwargs returns the appropriate chat template kwargs based on model and reasoning mode
 func getChatTemplateKwargs(model string, useReasoning bool) map[string]interface{} {
 	lower := strings.ToLower(strings.TrimSpace(model))
@@ -83,8 +104,11 @@ func (r *OpenAIRouter) setReasoningModeToRequestBody(requestBody []byte, enabled
 		}
 	}
 
+	family, param := getModelFamilyAndTemplateParam(model)
+
 	// Add chat_template_kwargs for reasoning mode
-	if kwargs := getChatTemplateKwargs(model, enabled); kwargs != nil {
+	kwargs := getChatTemplateKwargs(model, enabled)
+	if kwargs != nil {
 		requestMap["chat_template_kwargs"] = kwargs
 	} else {
 		delete(requestMap, "chat_template_kwargs")
@@ -96,17 +120,35 @@ func (r *OpenAIRouter) setReasoningModeToRequestBody(requestBody []byte, enabled
 		// This seems to be the default for openai/gpt-oss models
 		originalReasoningEffort = "low"
 	}
+	var appliedEffort string
 	if enabled {
 		// Use configurable reasoning effort based on category
 		effort := r.getReasoningEffort(categoryName)
 		requestMap["reasoning_effort"] = effort
+		appliedEffort = effort
 	} else {
 		requestMap["reasoning_effort"] = originalReasoningEffort
+		if s, ok := originalReasoningEffort.(string); ok {
+			appliedEffort = s
+		}
 	}
 
 	log.Printf("Original reasoning effort: %s", originalReasoningEffort)
 	log.Printf("Added reasoning mode (enabled: %v) and reasoning effort (%s) to request for model: %s", enabled, requestMap["reasoning_effort"], model)
 
+	// Record metrics for template usage and effort when enabled
+	if enabled {
+		// If we applied a known template param, record its usage
+		if kwargs != nil && param != "" {
+			metrics.RecordReasoningTemplateUsage(family, param)
+		} else if kwargs == nil && param == "reasoning_effort" {
+			// For GPT/GPT-OSS, we only set reasoning_effort
+			metrics.RecordReasoningTemplateUsage(family, param)
+		}
+		// Record which effort level was used for this family
+		metrics.RecordReasoningEffortUsage(family, appliedEffort)
+	}
+
 	// Serialize back to JSON
 	modifiedBody, err := json.Marshal(requestMap)
 	if err != nil {

src/semantic-router/pkg/extproc/request_handler.go

@@ -337,6 +337,9 @@ func (r *OpenAIRouter) handleModelRouting(openAIRequest *openai.ChatCompletionNe
 				// Check reasoning mode for this category
 				useReasoning, categoryName := r.getReasoningModeAndCategory(userContent)
 				log.Printf("Reasoning mode decision for this query: %v on [%s] model", useReasoning, matchedModel)
+				// Record reasoning decision metric with the effort that will be applied if enabled
+				effortForMetrics := r.getReasoningEffort(categoryName)
+				metrics.RecordReasoningDecision(categoryName, matchedModel, useReasoning, effortForMetrics)
 
 				// Track the model load for the selected model
 				r.Classifier.IncrementModelLoad(matchedModel)

src/semantic-router/pkg/metrics/metrics.go

@@ -192,6 +192,33 @@ var (
 		},
 		[]string{"model", "pii_type"},
 	)
+
+	// ReasoningDecisions tracks the reasoning mode decision outcome by category, model, and effort
+	ReasoningDecisions = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "llm_reasoning_decisions_total",
+			Help: "The total number of reasoning mode decisions by category, model, and effort",
+		},
+		[]string{"category", "model", "enabled", "effort"},
+	)
+
+	// ReasoningTemplateUsage tracks usage of model-family-specific template parameters
+	ReasoningTemplateUsage = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "llm_reasoning_template_usage_total",
+			Help: "The total number of times a model family template parameter was applied",
+		},
+		[]string{"family", "param"},
+	)
+
+	// ReasoningEffortUsage tracks the distribution of reasoning efforts by model family
+	ReasoningEffortUsage = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "llm_reasoning_effort_usage_total",
+			Help: "The total number of times a reasoning effort level was set per model family",
+		},
+		[]string{"family", "effort"},
+	)
 )
 
 // RecordModelRequest increments the counter for requests to a specific model
@@ -463,3 +490,34 @@ func InitializeBatchMetrics(config BatchMetricsConfig) {
 		)
 	})
 }
+
+// RecordReasoningDecision records a reasoning-mode decision for a category, model and effort
+func RecordReasoningDecision(category, model string, enabled bool, effort string) {
+	status := "false"
+	if enabled {
+		status = "true"
+	}
+	ReasoningDecisions.WithLabelValues(category, model, status, effort).Inc()
+}
+
+// RecordReasoningTemplateUsage records usage of a model-family-specific template parameter
+func RecordReasoningTemplateUsage(family, param string) {
+	if family == "" {
+		family = "unknown"
+	}
+	if param == "" {
+		param = "none"
+	}
+	ReasoningTemplateUsage.WithLabelValues(family, param).Inc()
+}
+
+// RecordReasoningEffortUsage records the effort usage by model family
+func RecordReasoningEffortUsage(family, effort string) {
+	if family == "" {
+		family = "unknown"
+	}
+	if effort == "" {
+		effort = "unspecified"
+	}
+	ReasoningEffortUsage.WithLabelValues(family, effort).Inc()
+}